Classes of Materials - Material Science and Engineering - Old Exam Paper, Exams of Materials science

Download Classes of Materials - Material Science and Engineering - Old Exam Paper and more Exams Materials science in PDF only on Docsity! - 1 - CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 2 Examinations 2010/11 Module Title: Material Science & Engineering Module Code: MECH6012 School: Mechanical & Process Engineering Programme Title: Bachelor of Engineering (Hons) in Mechanical Engineering Bachelor of Engineering (Hons) in Chemical and Biopharmaceutical Engineering Bachelor of Engineering (Hons) in Biomedical Engineering Bachelor of Engineering (Hons) in Structural Engineering Programme Code: EMECH_8_Y1 / EBIOM_8_Y1 / ECPEN_8_Y2 / EOMNI_8_Y1 CSTRU_8_Y1 External Examiner(s): Mr. John J. Hayes, Prof. Robin Clarke Internal Examiner(s): Dr Gerard Kelly Instructions: Answer any three questions. All questions carry equal marks Duration: 2 HOURS Sitting: Semester 2 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. - 2 - Q1. (a) Ceramics are intrinsically stronger than metals. However their use as an engineering material is limited. Identify 4 properties of ceramics which make them useful in an engineering context and outline how their properties are influenced by their atomic bonding arrangements. Suggest why they are they poor conductors. (6 marks) (b) Some classes of materials exhibit directionality in their properties. Identify which classes of engineering materials and explain why. (5 marks) (c) Briefly describe the relationship between bond energy and material properties such as Elastic modulus, CTE and Tm. (5 marks) (d) Identify 3 principle metal crystalline structures giving one example of each type. (6 marks) (e) Explain why we study material “defects” in engineering. Identify 3 types of “defects” commonly found in metals and explain the significance of one of these. Identify a situation where “defects” may be beneficial to a material’s properties (6 marks) (f) Explain what happens when a ductile material is subject to an externally applied force in a given direction. Why are fine grained materials less ductile than large grained materials? (5 marks) - 5 - Q4. a) Outline the conditions that must be satisfied for an alloy system to have unlimited solubility. (8 marks) b) The fracture toughness of a ceramic material may be improved if the ceramic matrix is reinforced with ceramic fibers. A materials designer has suggested that Al2O3 could be reinforced with 25% Cr2O3 fibers, which would interfere with the propagation of any cracks in the alumina. Both constituents have unlimited solubility in each other. The resulting composite is expected to operate under load at 2000 o C for several months. The Al2O3 - Cr2O3 phase is reproduced in figure Q4.1. Criticise the appropriateness or otherwise of this design. (13 marks) Figure Q4.1 Al2O3 - Cr2O3 phase diagram c) Describe with the aid of sketches where appropriate the effects of solid solution strengthening on the properties of a metal. (6 marks) d) From the phase diagram for the NiO-MgO binary system Figure Q4.2 describe a composition that can melt at 2600 o C but will not melt when placed into service at 2300 o C. Justify your answer. (6 marks) Figure Q4.2 Al2O3 - Cr2O3 phase diagram - 6 - Q5. (a) It is possible to harden the case of a steel by either of the two following processes which are commonly classified as “differential heat treatment” or “differential structure”. Describe both of these case hardening processes. (10 marks) (b) Describe how fick’s 2nd law can be applied to the carburising of a plain carbon steel. (8 marks) (c) Determine the carburising time necessary to achieve a carbon concentration of 0.45wt%C at a position 2mm into an iron carbon alloy that initially contains 0.2wt%C. The surface of the concentration is to be maintained at 1.3wt%C and the treatment is to be conducted at 1000 o C where D =1.93 x 10 -11 m 2 /s. (15 marks) TABLE 5-3 @ Error function values for Fick’s second law Argument Value of of the error function the error function x x ert 2./Dt 2\/Dt 0 0 0.10 0.1125 0.20 0.2227 0.30 0.3286 0.40 0.4284 0.50 0.5205 0.60 0.6039 0.70 0.6778 0.80 0.7421 0.90 0.7970 1.00 0.8427 1.50 0.9661 2.00 0.9953 Note that error function values are available on many software packages found on personal computers.